Stateful tests are tests against state machines. Ask: "are we testing a transition from one state to another?" or are we just testing "input/output".

An interaction between objects or roles (or both)

An obligation to perform a task (doing) or know information (knowing)

A contract is an agreement outlining the terms of a collaboration

A collection of responsibilities

The foundational measurements of structural software quality

A test double is a generic term to refer to any object that stands in for a production one during testing

A way to differentiate between mutable infrastructural dependencies

An abstraction that leaks details that it is supposed to abstract away

A software architecture rule that specifies the relationship between layers, namely that an inner layer should never rely on anything from an outer layer.

Data storage, change detection, and data flow.

An application where all the essential components are self-contained and deployed within a single process.

When the classes that describe the model and the classes that perform operations on the model are separate. The services contain all the domain logic while the the domain objects themselves contain practically none.

The more stable a component is, the more abstract it should be

Components dependencies should be in the direction of stability

One of several component design principles that states that the "dependency graph of components should have no cycles"

Any organization that designs a system (defined more broadly here than just information systems) will inevitably produce a design whose structure is a copy of the organization's communication structure.

An `Active Record` is a model that stores an in-memory representation of a database row or document.

Clean architecture refers to organizing the project so that it's easy to understand and easy to change as the project grows.

Generally speaking, there are 3.

The abstract factory pattern provides a way to encapsulate a group of individual factories that have a common theme without specifying their concrete classes.

'You aren't gonna need it'

Invariants are a form of ensuring data integrity of an object.

Classes that are complete with fully implemented methods.

A de-coupling technique where both high-level and low-level classes depend on the same abstraction, inverting the dependency relationship.